Dielectric substance



- Patented Apr. 1, 1930 UNITED STATES PATENT OFFICE m a. minus, or wxome, 01110, assrenon no man nIomnnsoN-comm, or

LOGKLAND, 01110, A conrona'rron or OHIO DIELECTRIC SUBSTAN No Drawing.

geneous manner, or .in a state of substantially ultimate dispersion in thebitumen. Reference is hereby made to U. S. Patent to Woodley No. 1,156,122, 0a. 12, 1915.

It is'the object of my invention toprovide a substance, which is moldable into various forms, and which has great tensile strength. when cold, and a large elastic limit, and

which is not affected by the action of hot or cold acid, is non-porous, will not swell, has

. a very large resistance to low' frequency electric currents, and is not affected when in the presence of electrolytic action.

26 Such a substance is fitted pre-eminently for molding into storage battery containers,

. into which compartments are formed to take the place of the present day individual rubber cell, the electrolyte and plates being set so directly into the said compartments.

In forming my new material, I use an as- I phalt which is a blend, preferablyhigh in gilsonite, so as to give cohesiveness and adhesiveness, and I incorporate into this asphalt a filler of mineral character, and a fibrous material, to give hardness and tensile strength. The exact nature of the asphalt or bitumen which is used, and the exact kind of mineral filler and of fibrous filler, may be varied to 40 suit different conditions, it being understood that in the following specification I am set-' ting forth one particular exampleofmy in-.

vention, giving preferred elements and treatment to gain the one special result in battery containers, and that in .the claims, which follow the specification, I desire to set forth'the invention inherent in the subject matter set forth.

The mineral filler used by me has advantages which are two-fold, over any oneof the Application-filed April 13', 1923. Serial No. 631,743.

inert earths. In the first place it is acid resistant, and resists electrolytic action, which is not alwaysthe same thing. In the second place, it is of fibrous character, and acts as a reinforcing material. 5

The ordinary chrysotile asbestos of commerce, whicha pears in fibrous form, is not resistant to aci action, and hence cannot be employed. I find, however, that amphibole asbestos, which is acid proof, can be used with great advantage. The amphibole asbestos roducts of today are almost never in fibrous orm, as when passed through the processes of segregating them from the rock in which they are found, the fibrous quality is almost as entirely destro ed, due to inherent fragility. When remove by a water flotation process, this asbestos is left in an excellent fibrous form, which form, however, is more or less lost by any ordinary methods of drying. 10

In myprocess, however, it is of advantage to have the asbestos wet, when immersed into the bituminous bath.

I have found that a form .of amphibole asbestos called actinolite, when removed by the TI water flotation' process, familiar to mineralogists, and left in the wet stage, and merely pressed into a moist cake, forms the best mineral filler that I can use.

As to the ordinary fiber filler, I em loy 0 any organic or vegetable fibers, which desire to 'have as long and tough as possible. The best fiber I have found to be a good clean cotton fiber.

I have discovered, however, that if I emfat ploy over about 14% of vegetable fiber, that the resulting product will not be acid resistant, or resistant to electrolytic action. By being acid resistant, I mean that the material formed up with a good bitumen, and the 'i' fiber intimately intermixed should not show marked discoloration in an acid bath, of 1.3 S. Glsulphuric acid at 125 degrees F. for 15 to 25 hours.

Particularly in battery containers, an tendency to show discoloration in the aci results in a depositing action on the plates, whereby they are covered with the gummy products liberated from the bitumen. The usual rubber cell will show discoloration, de-

charge by the service station or while in use,

while the composition described herein shows no discoloration after many hours of overcharge.

As a safety factor, I prefer to use around ten percent of fiber, although the more fiber incorporated, the greater physical resistance is given to the composition. Cotton fibres are the best which I have found because due to their length and strength, a smaller quantity by weight will produce better qualities, than larger quantities of other fibrous matter In one specific manufacturing-method I place hot asphalt in a mixer, and add thoroughly wetted asbestos fiber of the character noted, and operate the mixing blades until the asbestos is thoroughly dispersed or distributed throughout the bituminous mass. I then continue the heat until the water disappears. I- then add cotton fiber, with as little water as possible so long as each fiber is coated with the water, and continue the mixing action in the presence of heat to maintain the bitumen in molten condition. The fiber of cotton may be incorporated first, and the asbestos last, if desired.

The asbestos material does not pulverize when mixed in with the bitumen while wet, and does not act to grind up the vegetable fiber (cotton fiber). Also the degree of moisture, sufiicient' to merely film the surfaces of the fibers, speeds up the fibrating action, to

'the degree that less time is necessary to eliminate the aqueous content from the final prod not. The mixing should be carried to the extent of colloidal relation.

A mixture of fibres in bitumen similar to colloidal mixture results when the bitumen forms a complete coating on the fibres and a separating body between elementary fibres. This is accomplished by the Woodley patents of record in which the asphalt is imposed on the fibres by agitation thereof in the presence of the asphalt when it is gummy enough to form the means of liberating the elementary fibres from each other, due to the working thereof. If the fibres are wet, this cools the satur'ant, when it is of the type discussed in this specification, sufficiently to cause it to act in the manner noted.

' The difference between a mixture of fibres similar to a colloidal mixture, and a mere mixture of fibres and a binder, rests in the completeness of the external phase of the binder. A comparative test can be made up as follows which will indicate the result in a graphic way. First, saturate and coat a web of fibres with a given per cent of soft asphalt. Second, liquify some more of the soft asphalt, and mix the fibres up in it, until asmuch uniformity as possible is gained, using the same proportions. Third, take halfiof the mass'of the second test and let it cool oraddsome water, and proceed to mix further, so that the asphalt pulls like pulling candy and liberates the individual fibres. The result of the third process will have markedly different properties from the retained half of the second, and the second and third will have markedly different properties from the first.

The third step will present the feature of a colloidal mixture, and the term fibration has been coined to describe the. process.

The product produced is increased in value by submitting the same to high pressures, and quickly sets under pressure into a very compact mass, entirely non-porous.

It is readily moldable, and in one process I form it up between male and female mold parts into a battery container with a plurality of integrally formed plate chambers or cells.

I also mold insulation pieces, for electrical equipment, which can be done quickly and cheaply, forming a product equal to phenolic condensation products, at least from the point of View of low frequency currents.

The percent of asbestos fiber will varyv with the needs of the final product.- In my bat- .tery container, I may use approximately equal parts asbestos fiber and bitumen, and the remainder vegetable fiber, although the proportions will vary depending upon the bitumen used, and the purpose for which the product'is intended. By the term bitumen in my claims is meant an organic or hydro-carbon binder of which asphalt is one.

described, comprising bitumen, asbestos fibre in fibrous form, and of acid resistant character, and organic fibre, said organic fibre being less than'substantially 15% of the mass,

and said fibrous material being uniformly dispersed within the bitumen, and the individual fibres covered with the bitumen to'an extent comparative to colloidal mixture.

' 2. A composition of matter for the purpose described comprising bitumen intermixed with acid resistant mineral matter in finely divided form, andorganic fibre, said organic fibre being less than substantially 15% of the mass by weight, and said organic fibrous material being uniformly dispersed within the bitumen and the individual fibres covered with the bitumen and spaced from each other thereby'to an extent comparative to colloidal mixture, and the whole ma'ss molded 'under high pressure.

3. Amolded article for use in the presence of electrolytic 'action comprising bitumen with finely divided acid resistant mineral matter and organic fibre, said organic fibre being in proportion of 10% to 15% of the mass bywei ht, and uniformly dispersed in the bitumen and coated thereby to an extent comparative tocolloidal mixture.

4. A moulded article for iise in the presence I of electrolytic action comprising bitumen with finely divided acid resistant mineral matter of fibrous nature and Organic fiber, said organic fiber being less than substantially 15% of the mass by weight, and uniforn'l-v 1y dispersed in the bitumen and coated thereby to an extent comparative to colloidal mixture.

ALAN R. LUKENS. 

